Power plant boiler sand comprising discarded foundry sand, use of power plant boiler sand, method for producing power plant boiler sand and apparatus for producing power plant boiler sand

Abstract

Power plant boiler sand comprising a clay-based binder film (3) on the surface of a grain of sand (2). In addition, a method and apparatus for producing power plant boiler sand.

The invention claimed is: 
     
         1 . Power plant boiler sand comprising a clay-based binder film on the surface of a grain of sand, wherein the power plant boiler sand is formed from air- cooled discarded foundry sand comprising clay-based binder and from which a fine fraction has been separated, the fine fraction being a sand portion in a predetermined size range. 
     
     
         2 . The power plant boiler sand as claimed in  claim 1 , wherein the clay-based binder film is of bentonite. 
     
     
         3 . The power plant boiler sand as claimed in  claim 1 , wherein the discarded foundry sand is used in a circulating fluidized bed boiler or in a fluidized bed boiler. 
     
     
         4 . The power plant boiler sand as claimed in  claim 1 , wherein:
 the discarded foundry sand is used in a circulating fluidized bed boiler, and   wherein the grain size is 0.05-1 mm.   
     
     
         5 . A method of using discarded foundry sand comprising clay-based binder, the method comprising applying the discarded foundry sand as power plant boiler sand, wherein the discarded foundry sand is air cooled, and wherein a fine fraction is separated from the discarded foundry sand prior to the discarded foundry sand being applied as the power plant boiler sand, the fine fraction being a sand portion with a predetermined size range, the power plant boiler sand having a clay-based binder film. 
     
     
         6 . The method as claimed in  claim 5 , wherein the discarded foundry sand is used as a bed material in forming a combustion grate at a power plant. 
     
     
         7 . The method as claimed in  claim 5 , wherein the discarded foundry sand is used in a fluidized bed boiler. 
     
     
         8 . The method as claimed in  claim 7 , wherein grain size of the discarded foundry sand used with the fluidized bed boiler is 0.5-2 mm. 
     
     
         9 . The method as claimed in  claim 5 , wherein the applying includes using the discarded foundry sand in forming a mold. 
     
     
         10 . The method as claimed in  claim 5 , wherein the clay-based binder film is of bentonite. 
     
     
         11 . The method as claimed in  claim 5 , wherein the discarded foundry sand is used in a circulating fluidized bed boiler or in a fluidized bed boiler. 
     
     
         12 . The method as claimed in  claim 11 , wherein:
 the discarded foundry sand is used in a circulating fluidized bed boiler, and   wherein the grain size is 0.05-1 mm.   
     
     
         13 . The method as claimed in  claim 5 , wherein the discarded foundry sand is used in a circulating fluidized bed boiler. 
     
     
         14 . The method as claimed in  claim 13 , wherein grain size of the discarded foundry sand is selected based on the circulating fluidized bed boiler in which it is to be used. 
     
     
         15 . The method as claimed in  claim 13 , wherein the grain size is 0.05-1 mm. 
     
     
         16 . The method as claimed in  claim 15 , wherein the grain size is 0.1-0.5 mm. 
     
     
         17 . A method of making power plant boiler sand, the method comprising:
 receiving discarded foundry sand comprising a clay-based binder;   air cooling the discarded foundry sand;   separating a fine fraction from the discarded foundry sand, the fine fraction being a sand portion with a predetermined size range; and   providing the air-cooled discarded foundry sand with the fine fraction removed therefrom for use as the power plant boiler sand, the power plant boiler sand including a clay-based binder film from the clay-based binder in the discarded foundry sand.   
     
     
         18 . The method as claimed in  claim 17 , wherein the discarded foundry sand is used as a bed material in forming a combustion grate at a power plant. 
     
     
         19 . The method as claimed in  claim 17 , wherein the discarded foundry sand is used in a circulating fluidized bed boiler. 
     
     
         20 . The method as claimed in  claim 19 , wherein grain size of the discarded foundry sand is selected based on the circulating fluidized bed boiler in which it is to be used. 
     
     
         21 . The method as claimed in  claim 19 , wherein the grain size is 0.05-1 mm. 
     
     
         22 . The method as claimed in  claim 21 , wherein the grain size is 0.1-0.5 mm. 
     
     
         23 . The method as claimed in  claim 17 , wherein the discarded foundry sand is used in a fluidized bed boiler. 
     
     
         24 . The method as claimed in  claim 23 , wherein grain size of the discarded foundry sand used with the fluidized bed boiler is 0.5-2 mm. 
     
     
         25 . The method as claimed in  claim 17 , wherein the discarded foundry sand is used in forming a mold. 
     
     
         26 . The method as claimed in  claim 17 , wherein the clay-based binder film is of bentonite.